I playtest with my regular gaming group. They're a trusting bunch of louts who generally don't mind what's being played so long as I'm the one running the game, and they're willing to indulge me since I've published (exactly one) book before.

In between sessions, I revise the rules based on how the game played (or more specifically, how it failed to meet my expectations). Sometimes, if things are too problematic for a "quick fix," I shelve the project until I've had a chance to mull over whether or not the thing really needs to be published at all. I have several of these "works in progress" on ice currently.

I playtest either with known people or with stranger at Cons, informing them before starting that the game may be broken.I don't find there are any easier or harder part to playtest... usually the easier parts are those who already have a defined shape and are known to work.Whenever the game leads to the use of a part that is not already defined, I warn the players before starting with the untested mechanics.

There are two kinds of playtests, as far as I noticed so far: the strict mathematical/mechanicistic testing of single rules, to see if they actually work on a "engine" side, and a more complete gaming test that is a true game session with a developing fiction.The later is more delicate, as if a rule is broken, it screws the whole game and may upset the players if they don't know they're testing. I think this happens because roleplaying is engaging as an activity and it automatically build expectations. If these expectations result broken by the game itslef, this brings to frustration. And for sure, you want to avoid frustration.

About feedbacks... I accept and appreciate either direct feedbacks coming instinctively out of the game while it is played, and also global feedbacks reported at the end.I won't force one way or the other, because I think that feedbacks are better valued if they come in a natural form from the players. And there are players who prefer to report and comment immediately (and I am one of these, for example) and others who prefer to take notes and report at the end.Both ways of feedback work great, so I think everyone should be able to give their feedbacks in the way they prefer.

I've run into this before: "I saw the rules, but I figured I wouldn't follow them." That's not going to work here. The rules for each forum are inflexible and enforced.

I do think there's a solution that will benefit everyone. If you'd like the thread to continue, then I suggest posting a description of your own playtesting experiences for the game you're working on. That will provide a great foundation for addressing the questions you've asked so far. I encourage you do to so.